Little-Known Way to Create Luminosity Masks in Lightroom

Luminosity Masks are mainly associated with Adobe Photoshop but did you know you can easily make them in Lightroom too?

It’s no secret that Lightroom is mainly used for applying global raw adjustments. Sure, there are some tools, such as the HSL/Color tab, that allow you to make more targeted adjustments but in general, it’s not used for local changes.

That’s why many photographers include Photoshop in their workflow. There you can use layers and masks to target as specific areas of an image as you want. Luminosity Masks are a popular way of doing this.

Lightroom has neither layers nor masks but there’s still a way to create Luminosity Masks. This is only possible when using a Graduated Filter, Radial Filter, or Adjustment Brush. More precisely, it’s made using the Range Tool.

There’s even a little-known way to create a mask that’s more or less the same as what you can make in Photoshop. Let’s see how!

Note: This feature is only available in Lightroom CC.

What is a Mask in Lightroom?

Before creating the Luminosity Mask, you need to understand what a mask is. It’s a big part of Photoshop but not so much in Lightroom.

Lightroom has a few tools that contain some sorts of masks but they aren’t flexible and can’t be used for anything else than that specific adjustment.

Recommended Reading: Understanding Layers & Masks in Photoshop

There are, however, three tools that allow for a bit more advanced masking. More specifically, we’re talking about the Graduated Filter, Radial Filter, and Adjustment Brush. These tools make it possible to apply adjustments to specific areas of the image. 

For example, dragging a Graduated Filter from the top of the photo and down to the center tells Lightroom to apply its adjustments to the area above the bottom line. This can be considered a mask.

Hitting ‘O’ on your keyboard or checking the ‘Show Selected Mask Overlay’ box reveals a red overlay that shows exactly where the adjustments are added.

What is the Range Mask?

Simply put, the Range Mask is used to fine-tune a mask based on color, luminance, or depth. 

The Graduated Filter, Radial Filter, and Adjustment Brush are good when wanting additional flexibility in your post-processing workflow but they are quite basic.

Let’s say that we want to use the Graduated Filter to darken the sky. The mask is easily made by dragging a graduated filter from the top of the frame and down to the horizon. You can then use the exposure slider to darken the photo. 

The problem is that by doing this, we also darken unwanted areas. Either because they’re already dark, or because it would be unnatural to darken them. 

That’s where the Range Masks come in; You can use it to refine the mask created by the Graduated Tool and tell Lightroom to avoid adding the adjustment to certain areas. 

There are three options of how to refine the mask: Color, Luminance, and Depth. 

The Range Mask Luminance

It’s the Luminance method that’s used to create a Luminosity Mask in Lightroom. Creating a mask based on luminance values means that you can target areas based on their brightness.

I’ve written extensively about these types of masks in my eBook A Photographer’s Guide to Luminosity Masks, as it’s one of the most important masking techniques you can use in Photoshop but creating them in Lightroom is different. The Range Mask tool itself isn’t nearly as complex as what you make in Photoshop but the results are surprisingly good.

In Lightroom, you need to first create a Graduated Filter, Radial Filter or Adjustment Brush before accessing the Range Mask. For this purpose, I recommend using the Graduated Filter and placing it just below the photo. Doing so means it will affect the entire photo.

After creating the filter, you can find the Range Mask tool beneath filter’s sliders:

The Luminance Range Mask consists of the Range and Smoothness sliders but also has an Eyedropper Tool and a Show Luminance Mask checkbox. Let’s take a closer look at the slider and options:

View the Luminance Mask

It’s essential to view the mask while it’s being created. If not, you have no idea of which areas it’s targeting.

The most common option is to tick the Show Luminance Mask box and use the red overlay that’s identical to the one you have with the Graduated Filter, Radial Filter, or Adjustment Brush.

However, I don’t recommend this option when working with the Range Mask tool.

A much better option is to hold Option (Mac) or Alt (PC) while adjusting the Range slider. This reveals a monochrome overlay known as a grayscale mask; a mask that will be familiar to Photoshop users.

The mask might look confusing at first but how it works is that adjustments are only added in the white areas of the mask. Grey areas are affected at a lower opacity while black areas are left alone. 

The Range Slider

The Range slider is the most important part of creating a Luminosity Mask in Lightroom. It’s this slider that tells Lightroom to which tonal range your adjustments should be applied to.

Think of it as a histogram where the left side represents blacks and the right side represents whites. A value of 0 represents pure black and a value of 100 represents pure white.  

By default (with a setting of 0 and 100), the entire image is selected. Taking the right knob and reducing it to 50 means that only the shadows and Midtones are affected. 

I strongly recommend taking a moment to pull the slider back and forth while holding Option or Alt to see how the grayscale mask changes. Pay attention to what happens when you increase the left knob and what happens when you decrease the right one. What about when you pull them close together?

The Eyedropper Tool

Above the sliders, you find the Eyedropper Tool. This is connected to the Range slider and can be used to create a mask based on the luminance values of the spot you click. 

For example, clicking in a shadow adjusts the Range slider to only affect the dark parts of the image. while clicking the sun makes it affect only the highlights. 

Personally, I’m not a big fan of using the Eyedropper but it can be helpful when trying to understand how the Luminance Mask work. 

Of course, you can use both the Eyedropper and the Range slider together; start by selecting a tonal value with the Eyedropper, then fine-tune the mask using the Range slider. 

The Smoothness Slider

The Smoothness slider controls the transition between the selected and non-selected areas (i.e. the white and black parts of the mask). 

A lower smoothness leads to a harder transition while a higher value makes it soft. As with the Range slider, holding Alt (Mac) or Option (PC) while adjusting it reveals the monochrome mask overlay.

It’s often best to leave this as it is. Too extreme values in either direction tends to look bad and lead to strange artefacts.

Creating a Luminosity Mask in Lightroom

By now you probably have an idea of how it works but let me show you a couple quick examples of how you can create luminosity masks that targets the shadows, midtones, or highlights:

• Step #1: Create a Graduated Filter and place all of it just beneath the image (you can place it on the photo to but know that the Range Mask is then only affecting those areas)
• Step #2: Select the Luminance option from the Range Mask Tool
• Step #3: Hold Option (Mac) or Alt (PC) and move the Range slider.
  • Create a Highlights Mask: Move the left knob past 50. The further towards 100 you move it, the stricter the mask becomes (i.e., targeting just the brightest brights)
  • Create a Midtones Mask: Move both knobs towards the middle. The closer towards 50 they are, the stricter the mask becomes. A standard midtones mask is in the range of 35/65
  • Create a Shadows Mask: Move the right knob down below 50. The further towards 0 you move it, the stricter the mask becomes.
• Step #4: Apply adjustments using the Graduated Filter’s sliders.

That’s it. Not too difficult, right?

Conclusion

Using Luminosity Masks in Lightroom can be a game-changer for many as you can apply adjustments to the shadows, midtones, or highlights individually. You can even refine the mask to only include very specific tonal ranges.

This gives you greater control when processing an image and you’re able to apply techniques and effects that most think are only possible in more advanced photo editors.

Lightroom’s Luminosity Masks aren’t as flexible as what you’re able to achieve in Photoshop but it’s perfect for those who prefer using Lightroom for their entire workflow.

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